Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

Which process creates convection currents due to air density differences?

1. Radiation

2. Conduction

3. Convection

4. Evaporation

The correct answer is: Convection

Convection is the process responsible for the creation of convection currents due to air density differences. This process occurs when warmer air, which is less dense, rises, while cooler, denser air descends. As the warmer air rises, it expands and cools, leading to a drop in temperature and density, prompting it to sink again. This cycle creates a continuous movement of air, resulting in convection currents. In the context of atmospheric processes, this mechanism is key to various phenomena, including weather patterns and thermal regulation within the atmosphere. The differences in temperature cause variations in air pressure, further enhancing the movement of air and the establishment of convection cells. The other processes listed, such as radiation, conduction, and evaporation, do not primarily create convection currents. Radiation involves the transfer of energy through electromagnetic waves, conduction refers to heat transfer through direct contact between materials, and evaporation is the transition of liquid to gas, which can contribute to changes in humidity and temperature but does not directly involve the movement of air masses in the same manner as convection.